ABSORPTION BODY

Abstract: An absorption body (10) is disclosed which is suitable for use in sanitary napkins (16) or similar. The body includes at least one layer of an absorbent material and has a plurality of longitudinally extending embossed channels (12). In order to promote distribution of discharged body fluid across a considerable area of the absorption body, at least three channels (12) are present, and the layer of absorbent material provides the absorption body (10) with a basis weight of between about 80 and 240 g/m<2>, preferably between about 120 and 160 g/m<2>. The invention also relates to a method of manufacturing the absorption body.

Description: TITLE: Absorption Body TECHNICAL FIELD: The present invention relates to an absorption body, suitable for use in sanitary napkins or similar, according to the preamble of claim 1, and a method of manufacturing an absorption body according to the preamble of claim 10. BACKGROUND OF THE INVENTION: In order to fit comfortably to the wearer, sanitary napkins are often formed with an hour-glass shaped absorbent pad having a narrow waist region which fits between the thighs of the wearer. Due to the narrowness of the pad at the region at which discharged body fluid is first intended to contact the pad, there is an increased risk of leakage of body fluid at the side edges of the napkin in use. Many solutions have been proposed to address this problem. EP-A-0 249 405 describes a sanitary napkin having a raised thickened central region and a compression line on either side of the raised region. The raised thickened region increases the surface area of the napkin at the narrow waist region, whilst the compression lines inhibit the leakage of body fluid to the side edges of the napkin. In said document, the raised central region is between 10 and 40 mm thick. This may be considered as being too bulky by some potential wearers. In WO 90/06096, side-edge leakage is addressed by the provision of a sanitary napkin having an absorption body, the density of which increases continuously from the edge margins in towards the centre part thereof. The configuration of such a napkin does not however lend itself to mass production in continuous webs. A sanitary napkin liner is known from US-A-4 795 455 which is designed to be used with a conventional sanitary napkin with a view to provide more rapid fluid take up and reduced fluid strike back. To hinder undesired lateral transmission of body fluids, the liner is provided with an hour-glass shaped embossing. In addition, and to promote rapid fluid absorbency, the napkin liner is provided with an embossed central channel of some 6 mm width. This channel directs rapid deposits of fluid along the channel, the fluid then being quickly transmitted through the liner to the underlying conventional sanitary napkin. Whilst the thus disclosed napkin liner is relatively thin, it is intended to be used in conjunction with a conventional napkin. In addition, to function optimally, it must be centrally positioned with respect to the wearer. Similarly, US-A-4 624 666 describes a sanitary napkin having a central elongated channel for transporting body fluid generally in the elongated direction. Again, this napkin must be accurately positioned in order to function most effectively. A method is disclosed in US-A-4 840 692 for producing an absorption body notably meant for use in cases of urinary incontinence in women. In said document it is an object to avoid using compressions in the body since these are said to slow down the rate of absorption of fluid. Instead, channels are formed in a pad of absorbent material by a working of cutting or milling. The pad is suitably 2 to 7 mm thick and the channels are said to need a width of at least 4 mm in order to facilitate distribution and absorption of the discharged fluid. SUMMARY OF THE INVENTION: It is therefore an object of the invention to provide an absorption body, primarily though not exclusively for use in sanitary napkins, which body lends itself to economic mass production techniques, resists side leakage and is thinner than conventional napkins. This object is achieved in accordance with the present invention by an absorption body having the features of Claim 1. Such an absorption body can be manufactured using the method according to claim 10. The combination of a plurality of longitudinally extending channels and the specified absorbent material allows for an optimal distribution of discharged body fluid across a considerable area of the absorption body. Since the fluid is more evenly distributed, the absorption body can be made relatively thin and the risk of uncomfortable rewetting is accordingly reduced. Advantageous embodiments of the absorption body and its method of manufacture are detailed in the respective dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS: The invention will now be described in greater detail by way of example only and with reference to the attached drawings, in which Fig. 1 is a schematic perspective view of an absorption body according to the invention; Fig. 2 is a schematic perspective view of a sanitary napkin, the topsheet of which is partially cut away to reveal the absorption body according to the invention, and Fig. 3 shows a peripheral region of an embossing roller used in the production of the absorption body according to the invention. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT: Referring to Fig. 1, reference numeral 10 generally denotes an absorption body incorporating the principles of the present invention. A preferred material for the absorption body 10 is airlaid latex-bonded paper. The principles of the invention may, however, be successfully realized with an absorption body employing a low density, thermally bonded airlaid paper comprising a mixture of absorbent fibres and non-wettable polymeric conjugate fibres. The absorption body 10 may be made from a single layer of absorbent material or may be laminated. In accordance with the invention, the layer of absorbent material provides the absorption body with a basis weight of between about 80 and 240 g/m 2 , preferably between about 120 and 160 g/m 2 . Preferably, though, the absorption body is a laminate of two or more layers of absorbent material with lamination taking place between a pair of heated rollers. A particular advantage of having a laminated absorption body is that the individual layers of absorbent material which make up the body can be thinner than if the body were made from a single layer. This implies that greater lengths of material can be wound onto feed rolls which supply the absorbent material to the heated rollers, thereby reducing the frequency with which the feed rolls have to be changed. In the case when the absorption body consists of two layers of absorbent material, each layer suitably has a basis weight of between about 60 and 100 g/m 2 . Similarly, when the absorption body consists of three layers of absorbent material, each layer also suitably has a basis weight of between about 60 and 100 g/m 2 . In accordance with the present invention, the absorption body 10 is provided with at least three longitudinally extending embossed channels 12. Between adjacent channels, there are thereby formed longitudinally extending absorbent rib portions 14. Preferably, and as shown in Fig. 1, the channels 12 are more than three in number and are uniformally spaced across substantially the entire width of the absorption body. This allows the absorption body 10 to be made as a continuous web, with individual absorption bodies then being cut out therefrom. The primary purpose of the channels 12 is to aid the distribution of discharged body fluid across a considerable surface area of the absorption body 10. Tests have shown that good results are obtained if each of the embossed channels has a base width of between about 0.7 and 2.0 mm, preferably between about 0.8 and 1.2 mm, most preferably about 1 mm. The channels 12 may be separated by a distance of between about 1.5 and 8.0 mm. However, to ensure that the risk of side leakage is minimized, it is preferable if the channels are separated by a distance of between about 2.5 and 3.5 mm. Since the absorption body of the present invention is capable of distributing fluid across a considerable surface area, there is a reduced risk of a particular region of the body from becoming saturated earlier than other regions. It is therefore possible to make the absorption body thinner than conventional absorption bodies of the same material, whilst still maintaining substantially the same absorption capacity. When used in a sanitary napkin, for example, the absorption body 10 may have a thickness of between 0.5 and 1.2 mm, preferably between 0.8 and 1.1 mm. In the case when the absorption body consists of a triple laminate, the thickness may go up to 1.5 mm. In Fig. 2 there is illustrated a sanitary napkin 16 which incorporates the absorption body 10 of the present invention. The sanitary napkin 16 comprises a topsheet 18 and a liquid-impermeable bottom sheet 20, with the absorption body 10 sandwiched therebetween. The topsheet 18 is intended to face the body of the wearer when the napkin is worn and may be made from a multi-apertured plastics film of the type disclosed in US-A-4 626 254. As is evident from Fig. 2, the topsheet 18 and the bottom sheet 20 completely enclose the absorption body 10 to leave a peripheral margin 22 which is not occupied by the absorption body 10. The topsheet and the bottom sheet are laminated, preferably using an adhesive or, alternatively, using ultrasonic or thermobonding, along the peripheral margin 22 to thereby securely locate the absorption body within the napkin. As is known in the art, the sanitary napkin 16 may be provided with one or more (not shown) strips of adhesive on the outer surface of the bottom sheet 20 to aid in the location of the napkin in the panties of the wearer. The strips of adhesive may of course be covered with a protective release strip which is provided to protect the adhesive from contamination and unintended adhesion prior to use. Similarly, the napkin 16 may have a pair of laterally positioned wings 24 with adhesive strips 26 on the portion of the bottom sheet 20 forming a part of said wings. In Fig. 3, a peripheral region 30 of an embossing roller is shown which is used in the production of the absorption body according to the invention. The embossing roller is provided with a plurality of raised portions 32, each raised portion 32 comprising a pair of lateral side surfaces 34 converging towards a substantially flat peak 36. The number, size and spacing of the raised portions 32 determines the number, size and spacing of the channels 12 in the absorption body 10 when absorbent material is passed between the embossing roller and a smooth anvil roller. Typically, each substantially flat peak 36 may have a width w of between about 0.7 mm and 2.0 mm, preferably between about 0.8 and 1.2 mm, and most preferably about 1 mm. The height h of the raised portions 32 is dependent on the desired thickness of the finished absorption body, though is typically about 1 mm. The lateral side surfaces 34 advantageously converge towards the peak 36 at an included angle of between 45° and 75°, preferably about 60°. The spacing, or pitch p, between the raised portions 32 may typically lie between about 3 and 5 mm, preferably about 4 mm. In order to aid the formation of the embossed channels 12, it is advantageous if the embossing process be conducted using an embossing roller surface temperature of about 120°C to 150°C, an anvil roller surface temperature of about 50°C to 90°C, and an embossing pressure of between about 300 and 500 N/linear mm, preferably about 400 N/linear mm. These temperatures and pressures are sufficient to ensure satisfactory lamination of the absorption body when a plurality of layers of absorbent material are fed simultaneously through the pair of rollers. The feed rate of the absorbent material through the rollers is primarily dependent on the thermal absorption properties of the absorbent material, though the number of layers, the temperature of the rollers and the embossing pressure also need to be considered. A suitable feed rate can typically lie between about 15 and 250 m/minute. The present invention is not restricted to that described above and shown in the drawings, but may be varied within the scope of the appended claims. For example, the channels 12 need not be straight, i.e. they may be given a wave- shaped longitudinal form. In addition, the spacing between the channels need not necessarily be uniform. Instead, the spacing may vary across the width of the absorption body; with e.g. narrow channels in the middle region of the absorption body and wider channels towards the lateral sides of the body. In order to improve the absorption properties of the body, it is feasible that super-absorbent granulates or fibres be included in the absorption body. In such a case, the absorption body suitably has a basis weight of between about 110 and 170 g/m 2 .

Claims: What is claimed is: 1. An absorption body (10) suitable for use in sanitary napkins (16) or similar, said body comprising at least one layer of an absorbent material and presenting a plurality of longitudinally extending embossed channels (12) , c h a r a c t e r i z e d in that said channels (12) are at least three in number and in that said at least one layer of absorbent material provides the absorption body (10) with a basis weight of between about 80 and 240 g/m 2 , preferably between about 120 and 160 g/m 2 . 2. The absorption body according to claim 1, c h a¬ r a c t e r i z e d in that said body (10) is a laminate of two or more layers of absorbent material. 3. The absorption body according to claim 2, c h a¬ r a c t e r i z e d in that said body (10) comprises two layers of absorbent material, each layer having a basis weight of between about 60 and 100 g/m 2 . 4. The absorption body according to claim 2, c h a¬ r a c t e r i z e d in that said body (10) comprises three layers of absorbent material, each layer having a basis weight of between about 60 and 100 g/m 2 . 5. The absorption body according to any one of the preceding claims, c h a r a c t e r i z e d in that said body (10) has a thickness of between 0.5 and 1.2 mm, preferably between 0.8 and 1.1 mm. 6. The absorption body according to any one of the preceding claims, c h a r a c t e r i z e d in that each of said embossed channels (12) has a base width of between about 0.7 and 2.0 mm, preferably between about 0.8 and 1.2 mm, most preferably about 1 mm. 7. The absorption body according to any one of the preceding claims, c h a r a c t e r i z e d in that said channels (12) are uniformally spaced and separated by a distance of between about 1.5 and 8.0 mm, preferably between about 2.5 and 3.5 mm. 8. The absorption body according to claim 7, c a¬ r a c t e r i z e d in that said channels (12) are uniformally spaced across substantially the entire width of the absorption body (10) . 9. The absorption body according to any one of the preceding claims, c h a r a c t e r i z e d in that the material of the absorption body includes a super-absorbent substance and in that the material provides the absorption body (10) with a basis weight of between about 110 and 170 g/m 2 . 10. A method of manufacturing an absorption body (10) suitable for use in sanitary napkins (16) or similar, said body comprising at least one layer of an absorbent material and presenting a plurality of longitudinally extending embossed channels (12) , said method c h a r a c t e r- i z e d in that said at least one layer of an absorbent material provides the absorption body (10) with a basis weight of between about 80 and 240 g/m 2 , preferably between about 120 and 160 g/m 2 , and in that said at least one layer of an absorbent material is passed between an embossing roller and an anvil roller, with said embossing roller being provided with at least three raised portions (32) to thereby create a corresponding number of channels (12) in the absorption body (10) . 11. The method according to claim 10, c h a r a c- t e r i z e d in that the surface of said embossing roller is maintained at a temperature of between about 120°C and 150°C, and in that the surface of said anvil roller is maintained at a temperature of between about 50°C and 90°C. 12. The method according to claim 10 or 11, c h a- r a c t e r i z e d in that said raised portions (32) on the embossing roller each present a substantially flat peak (36) having a width (w) of between about 0.7 mm and 2.0 mm, preferably between about 0.8 and 1.2 mm, most preferably about 1 mm, and in that said raised portions have a height (h) of about 1 mm. 13. The method according to any one of claims 10 to 12, c h a r a c t e r i z e d in that said at least one layer of an absorbent material is fed between the anvil roller and the embossing roller at a rate of about 15 to 250 m/minute. 14. The method according to any one of claims 10 to 13, c h a r a c t e r i z e d in that an embossing pressure of between about 300 and 500 N/linear mm, preferably about 400 N/linear mm, is used. 15. The method according to any one of claims 10 to 14, ' c h a r a c t e r i z e d in that said embossing roller is provided with a plurality of substantially uniformally spaced raised portions (32) across substantially its entire width. 16. A sanitary napkin incorporating the absorption body according to any one of claims 1 to 9. 17. A sanitary napkin incorporating the absorption body manufactured by the method according to any one of claims 10 to 15.

Inventors: JOHANSSON DAN, LINDQUIST BENGT, VASTAG EVA, JOHANSSON, DAN, LINDQUIST, BENGT, VASTAG, EVA
Applicants: JOHANSSON DAN, LINDQUIST BENGT, MOELNLYCKE AB, VASTAG EVA, JOHANSSON, DAN, LINDQUIST, BENGT, VASTAG, EVA
Application year: 1994
Main classification: A61F13
IPC codes: A61F13, B31F1, D06C23